The most concerning versions of the virus are not simply mutating—they’re mutating in similar ways.
For most of 2020, the coronavirus that causes COVID-19 jumped from human to human, accumulating mutations at a steady rate of two per month—not especially impressive for a virus. These mutations have largely had little effect.
But recently, three distinct versions of the virus seem to have independently converged on some of the same mutations, despite being thousands of miles apart in the United Kingdom, South Africa, and Brazil. (A mutation is a genetic change; a variant is a virus with a specific set of mutations.) The fact that these mutations have popped up not one, not two, but now three times—that we know of—in variants with unusual behavior suggests that they confer an evolutionary advantage to the virus. All three variants seem to be becoming more common. And all three are potentially more transmissible.